Roll-operated automatic musical instruments have been used and enjoyed for well over a century. By "roll-operated", it is intended to categorize the type of automatic musical instrument in which a punched paper roll travels from a pay-off spool on which the roll is stored to a take-up spool, passing over a tracker bar in the process to "read" the roll. Such an instrument in the broad class is exemplified by the ubiquitous 88-note (earlier, 65-note) "player piano" and its more sophisticated development, the reproducing piano of which the best known systems in the United States are the Ampico (in "A" and "B" variants), the Duo-Art and the Welte-Licensee. (Reproducing piano roll playing mechanisms, carefully restored and incorporated into a fine piano, are capable of recreating the playing of great artists of the past to an astonishing degree.)
However, numerous other roll-operated musical instruments have been manufactured in the past and have been preserved and restored. These include player organs, nickelodeons, orchestrions, etc. Most of these instruments employ tracker bars which have an array of horizontally spaced (most commonly, but not exclusively, nine holes per inch) holes to "read" the punched holes in a performance roll which define the note or notes to be played at a given instant (as a given note perforation in the paper passes over the corresponding hole in the tracker bar) and, in some instances, such as reproducing pianos, also to specify pedaling, instantaneous volume and other performance and control information. Often, one hole position will serve to define an "end-of-roll" condition to trigger a reroll operation in which the roll is rapidly rewound onto the pay-out spool (which is typically removable to permit playing different performances).
Some heavier-duty automatic musical instruments, such as large orchestrions and some band organs, employ a variant of the performance roll constituting a "book" of heavy, cardboard-like punched pages which are sequentially unfolded, fed across a tracker bar and refolded. However, the principal of operation is the same as that of the previously described performance roll.
In typical operation, a given tracker bar hole is normally covered as the music roll traverses from the pay-out spool to the take-up spool, but may be uncovered from time-to-time by suitably positioned perforations in the roll as the performance proceeds. When the hole is uncovered, atmospheric pressure is admitted into the tracker bar hole which is connected by tubing to the underside of a valve pouch. The valve pouch has a vacuum on its upper side, and the individual cavity beneath a valve pouch receives a vacuum supply from the upper side through a small bleed orifice. Thus, when a perforation in the moving paper roll uncovers a hole in the tracker bar, the underside of the corresponding pouch changes to atmospheric pressure, and the pouch springs upwardly because of the sudden pressure differential placed across it. This action can be used to throw a valve to, for example, admit vacuum to a striker pneumatic, thus causing it to collapse and, through mechanical coupling to the action of the instrument, play a note. When the perforation in the roll passes the tracker bar hole, it is closed off such that the pouch drops as a result of the bleed admitting vacuum to its underside, and the valve is deactivated.
While some automatic musical instruments operate on pressure rather than vacuum, the principal of selectively admitting atmospheric pressure to the holes of a tracker bar as a performance roll traverses it remains the same. In addition, some automatic musical instrument valves work on a "lock-and-cancel" basis in which exposure of one tracker bar hole fires a valve which remains "on" until exposure of a different tracker bar hole shuts it "off". Again, the relationship of a performance roll's perforations to the tracker bar's holes remains the same.
For a comprehensive survey of pneumatically operated musical instruments, one may refer to Encyclopedia of Automatic Musical Instruments by Q. David Bowers (Vestal Press--1972) and Treasures of Mechanical Music by Arthur A. Reblitz and Q. David Bowers (Vestal Press--1981). Similarly, for a superior treatment of the technology of such instruments, particularly player and reproducing pianos, reference may be taken to Player Piano Servicing and Rebuilding by Arthur A. Reblitz (Vestal Press--1985).
Notwithstanding the enjoyment of listening to a good roll-recorded performance on a fine tracker bar based automatic musical instrument, those skilled in the art are well aware of numerous drawbacks to these systems resulting from the fundamental requirement to use, handle and store the rolls themselves.
First, original rolls are now in the range of 60-90 years old, and most of them are fragile, even unplayable, because the acts of mounting, playing and rewinding a roll can destroy it a single play. As a result, and in accordance with renewed interest in automatic musical instruments which itself has been ongoing for some 40 years, a small industry has been devoted to supplying "recuts"; i.e., modem copies of original performance rolls. Recuts themselves are open to a number of objections. In most instances, the copying procedure has resulted in slight variations in the positions of perforations along the length of a roll resulting in a temporal distortion of the recorded performance. (However, a very few recuts have been made so carefully that no fault can be found on this point.) Then, the thickness of the paper is different, usually thicker, than the original rolls which can result in a subtle distortion in tempo because the diameter of the roll accumulating on the take-up spool (which is driven at a constant rate of revolution) builds up at a different rate than with the original rolls, typically resulting in an unintended increase in tempo of the music as a given performance proceeds. (Again, a very few recuts carefully take this variable into account and use paper of appropriate thickness.)
Second, original rolls in good condition have become very expensive, and recuts themselves are expensive.
Third, even a relatively small collection of rolls takes up considerable storage space.
Fourth, the length of a musical performance which can be recorded on a music roll is decidedly limited, typically to a single musical composition or even a fraction of a longer composition. Some systems permit the use of "jumbo" rolls which can include upwards of twenty minutes of performance from a single roll, but often even the original jumbo rolls were assembled from a plurality of shorter rolls which introduced a serious tempo distortion because of the increased thickness of build up on the take-up spool as a roll progressed. Modern "jumbo" rolls made up of copies of a plurality of original rolls can be particularly offensive because of this reason.
Fifth, while some collectors enjoy the ritual of finding, loading, playing, rewinding and returning to storage each roll, most collectors tire of this process and would gladly enjoy the facility to be able to play electronically recorded rolls on their original automatic musical instruments.
Over the years, various systems have been designed to achieve this end. Typically, solenoid-operated valves have been inserted in each tubing line between the tracker bar and the respective tubing destinations. Electronically recorded rolls (for example, on cassette tapes or compact disks) are then employed with suitable interface electronics to simulate the opening and closing of the individual tracker bar holes as if a roll were playing. However, these systems have been difficult to install, often requiring the services of a professional in the field, and, further, typically require alteration to the original instrument. Still further, if it is desired to move such a system to a different instrument, it must be "deinstalled" (with suitable restoration to the instrument) and then installed in the second instrument with the same difficulty and objections previously noted. Further yet, in some instruments, there is insufficient room to install such a system or insufficient room to effect the installation without spoiling the aesthetics of the instrument.